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Re: Avian flight stroke origin

One of the reasons the dichotomy was thought to exist (and still does today) 
was a mistaken assumption that arboreal and terrestrial launch in birds are 
fundamentally different, which they are not. In fact, they are almost identical.


--Mike H.

Sent from my iPhone

On Aug 11, 2011, at 3:42 AM, "Dr Ronald Orenstein" <ron.orenstein@rogers.com> 

> This raises a point that I still do not understand. Why is it assumed that 
> arboreality and terrestriality are such vastly different ways of life that 
> entire lineages can be assumed to have been  one or the other, when living 
> birds, mammals, reptiles etc clearly show that this is not the case?  In 
> birds alone we have genera containing both highly arboreal and purely 
> terrestrial species (eg Coracina, whose members are mostly arboreal but which 
> includes the terrestrial Ground Cuckoo-Shrike C. maxima), families such as 
> Corvidae with secondarily-terrestrial genera like Podoces, etc.
> It can be objected that these are much better fliers than maniraptorids, and 
> that getting into a tree does not require special climbing adaptations if you 
> can fly there. In that case, what about (say) squirrels, which range 
> similarly from the ground to the treetops and include gliding species. If a 
> marmot and a flying squirrel can be close relatives, why can't dromaeosaurids 
> (say) have included a similar mixture?
> Further, as I have said here before, a number of birds, including 
> particularly the cracids, can shift back and forth between trees and the 
> ground with ease, and others feed on the ground and nest in trees (including 
> such unlikely tree-dwellers as ducks). Could there have been tree- or 
> cavity-nesting dinosaurs?  We'd be unlikely to find fossil evidence on the 
> point. 
> Also, even flightless or near-flightless species of birds can get up into a 
> tree without having climbing-adapted front limbs. It's quite amazing to see 
> the ability some birds have of getting around in trees by simply jumping from 
> branch to branch, and if the trees have limbs near the ground they can reach 
> the canopy in this way too. A good example might be the Kokako (Callaeas 
> cinerea) of New Zealand, which is a fairly weak flyer (and, oddly for a 
> passerine, a folivore), but which is almost if not entirely arboreal; it 
> tends to leap upwards and fly/glide downwards. 
> Ronald Orenstein 
> 1825 Shady Creek Court
> Mississauga, ON
> Canada L5L 3W2
> On 2011-08-11, at 1:36 AM, Tim Williams <tijawi@gmail.com> wrote:
>> Jaime Headden <qi_leong@hotmail.com> wrote:
>>> So close! From the title: "Assessing Arboreal Adaptations of Bird 
>>> Antecedents."
>>> AVIAN antecedents. It would have been so beautiful!
>> It's not just the alliteration that falls short.  I also found myself
>> disagreeing with quite a few of the conclusions in the paper.
>> Nevertheless, it's pleasing to see Dececchi & Larsson (2011) refute
>> the hypothesis that the ancestors of birds were specialized for
>> arboreality.  That's always good to see, because this is the central
>> plank of the BANDit's scenario-driven approach to the evolution of
>> avian flight.  Dececchi & Larsso single out the splayed, quadrupedal
>> posture of "four-winged" gliding theropods for special criticism.